feat: Add secure audio cooperation and microphone gain control

invictus737 · s1lviu · commit d68fa160b1ac · 2025-08-29T20:29:12.000+03:00
Two major enhancements for improved iOS audio handling:

## 🔒 Secure Audio Cooperation
- Prevent audio leakage from other apps during PTT transmission
- Dynamic audio session management: ducking during PTT, mixing when idle
- Enhanced security validation in audio input processing
- Smooth transitions between cooperative and exclusive audio modes

### Changes:
- IOSAudioManager: Added ducking/mixing session configuration methods
- ReflectorClient: Secure PTT flow with session mode switching
- AudioEngine: Security validation to prevent non-microphone audio transmission

## 🎚️ Microphone Gain Control (-20dB to +20dB)
- Real-time adjustable microphone gain slider in UI
- Integrates with existing iOS 24dB base gain processing
- Professional iOS-style slider with live dB value display
- Thread-safe gain updates between UI and audio engine

### Changes:
- ReflectorClient: Added micGainDb Q_PROPERTY with bounds checking
- AudioEngine: Configurable gain application in input processing
- Main.qml: Native iOS slider control positioned above connect button

### Technical Details:
- Security: Only microphone input transmitted over radio network
- Cooperation: Music/podcast apps resume after PTT release
- Flexibility: -20dB to +20dB range with 0.5dB precision
- Safety: Automatic bounds checking and soft limiting
diff --git a/iOS/AudioEngine.cpp b/iOS/AudioEngine.cpp
@@ -771,6 +771,16 @@ void AudioEngine::onAudioInputReadyRead()
         return;
     }
     
+#if defined(Q_OS_IOS)
+    // SECURITY CHECK: Verify audio session is in secure mode during PTT
+    // This prevents other apps' audio from being transmitted over the radio network
+    if (!ios_isAudioSessionSecure()) {
+        qWarning() << "AudioEngine: SECURITY WARNING - Audio session not in secure mode during PTT, dropping audio data";
+        qWarning() << "AudioEngine: This prevents other apps' audio from being transmitted over radio";
+        return;
+    }
+#endif
+    
     QByteArray pcmData = m_audioInputDevice->readAll();
     if (pcmData.isEmpty()) {
         qDebug() << "AudioEngine::onAudioInputReadyRead - No data available";
@@ -820,9 +830,11 @@ void AudioEngine::onAudioInputReadyRead()
         
 #if defined(Q_OS_IOS)
         // iOS-specific input gain boost to compensate for low microphone levels
-        // Apply aggressive gain to match Android -6dB levels (iOS typically -30dB without boost)
-        // Target: 24dB boost (16x amplification) to go from -30dB to -6dB
-        const float iosInputGain = 16.0f;
+        // Apply base gain (24dB/16x) plus user-configurable mic gain
+        // Base: 24dB boost (16x amplification) to go from -30dB to -6dB
+        // User: Additional -20dB to +20dB adjustment
+        const float iosBaseGain = 16.0f;
+        const float totalGain = iosBaseGain * m_micGainLinear;
         
         // Debug: Log input levels periodically for Int16 format
         static int debugCounterInt16 = 0;
@@ -831,15 +843,15 @@ void AudioEngine::onAudioInputReadyRead()
             for (int i = 0; i < monoSamples; ++i) {
                 maxLevel = std::max(maxLevel, std::abs(m_reusableFloatBuffer[i]));
             }
-            qDebug() << "iOS Int16 input level before gain:" << maxLevel << "after gain:" << (maxLevel * iosInputGain);
-            qDebug() << "iOS Int16 gain applied: 16x (" << (20 * log10(iosInputGain)) << "dB)";
+            qDebug() << "iOS Int16 input level before gain:" << maxLevel << "after gain:" << (maxLevel * totalGain);
+            qDebug() << "iOS Int16 total gain applied:" << totalGain << "x (Base: 24dB + Mic:" << m_micGainDb << "dB)";
             if (maxLevel < 0.001f) {
                 qWarning() << "iOS WARNING: Input level extremely low!" << maxLevel << "- Check microphone permissions";
             }
         }
         
         for (int i = 0; i < monoSamples; ++i) {
-            float sample = m_reusableFloatBuffer[i] * iosInputGain;
+            float sample = m_reusableFloatBuffer[i] * totalGain;
             // Professional soft limiting for high-gain scenarios
             // Use tanh() for smooth saturation instead of hard clipping
             if (std::abs(sample) > 0.9f) {
@@ -881,9 +893,11 @@ void AudioEngine::onAudioInputReadyRead()
         
 #if defined(Q_OS_IOS)
         // iOS-specific input gain boost to compensate for low microphone levels
-        // Apply aggressive gain to match Android -6dB levels (iOS typically -30dB without boost)
-        // Target: 24dB boost (16x amplification) to go from -30dB to -6dB
-        const float iosInputGain = 16.0f;
+        // Apply base gain (24dB/16x) plus user-configurable mic gain
+        // Base: 24dB boost (16x amplification) to go from -30dB to -6dB
+        // User: Additional -20dB to +20dB adjustment
+        const float iosBaseGain = 16.0f;
+        const float totalGain = iosBaseGain * m_micGainLinear;
         
         // Debug: Log input levels periodically for Float format
         static int debugCounterFloat = 0;
@@ -892,15 +906,15 @@ void AudioEngine::onAudioInputReadyRead()
             for (int i = 0; i < monoSamples; ++i) {
                 maxLevel = std::max(maxLevel, std::abs(m_reusableFloatBuffer[i]));
             }
-            qDebug() << "iOS Float input level before gain:" << maxLevel << "after gain:" << (maxLevel * iosInputGain);
-            qDebug() << "iOS Float gain applied: 16x (" << (20 * log10(iosInputGain)) << "dB)";
+            qDebug() << "iOS Float input level before gain:" << maxLevel << "after gain:" << (maxLevel * totalGain);
+            qDebug() << "iOS Float total gain applied:" << totalGain << "x (Base: 24dB + Mic:" << m_micGainDb << "dB)";
             if (maxLevel < 0.001f) {
                 qWarning() << "iOS WARNING: Input level extremely low!" << maxLevel << "- Check microphone permissions";
             }
         }
         
         for (int i = 0; i < monoSamples; ++i) {
-            float sample = m_reusableFloatBuffer[i] * iosInputGain;
+            float sample = m_reusableFloatBuffer[i] * totalGain;
             // Professional soft limiting for high-gain scenarios
             // Use tanh() for smooth saturation instead of hard clipping
             if (std::abs(sample) > 0.9f) {
@@ -1320,4 +1334,19 @@ void AudioEngine::AudioLimiter::processAudio(float* samples, int count) {
         // Apply gain reduction to input sample
         samples[i] = outputGain_ * samples[i] * gainReduction;
     }
+}
+
+void AudioEngine::setMicGainDb(double gainDb)
+{
+    // Clamp gain to -20dB to +20dB range for safety
+    gainDb = qBound(-20.0, gainDb, 20.0);
+    
+    if (qAbs(m_micGainDb - gainDb) < 0.1) return; // Avoid unnecessary updates
+    
+    m_micGainDb = gainDb;
+    
+    // Convert dB to linear gain factor: gain_linear = 10^(dB/20)
+    m_micGainLinear = static_cast<float>(std::pow(10.0, gainDb / 20.0));
+    
+    qDebug() << "AudioEngine: Microphone gain updated to" << gainDb << "dB (linear:" << m_micGainLinear << ")";
 }
diff --git a/iOS/AudioEngine.h b/iOS/AudioEngine.h
@@ -67,6 +67,7 @@ public slots:
     void onActivityPaused();
     void onActivityResumed();
     void allSamplesFlushed();
+    void setMicGainDb(double gainDb);
 
 signals:
     void audioReadyChanged(bool ready);
@@ -117,6 +118,10 @@ private slots:
     bool m_audioFocusPaused = false;
     QDateTime m_lastAudioWrite;
     
+    // Microphone gain control (-20dB to +20dB)
+    double m_micGainDb = 0.0;
+    float m_micGainLinear = 1.0f;
+    
     // Pre-allocated buffers for performance optimization
     std::vector<float> m_reusableFloatBuffer;
     std::vector<unsigned char> m_reusableOpusBuffer;
diff --git a/iOS/Main.qml b/iOS/Main.qml
@@ -318,6 +318,111 @@ Item {
                     }
                 }
                 
+                // Microphone Gain Control
+                ColumnLayout {
+                    Layout.fillWidth: true
+                    Layout.topMargin: 6
+                    Layout.bottomMargin: 3
+                    
+                    RowLayout {
+                        Layout.fillWidth: true
+                        
+                        Label {
+                            text: "Mic Gain:"
+                            color: isDarkMode ? "#FFFFFF" : "#000000"
+                            font.pixelSize: Qt.platform.os === "ios" ? 16 : 14
+                        }
+                        
+                        Item { Layout.fillWidth: true } // Spacer
+                        
+                        Label {
+                            text: ReflectorClient.micGainDb.toFixed(1) + " dB"
+                            color: isDarkMode ? "#8E8E93" : "#666666"
+                            font.pixelSize: Qt.platform.os === "ios" ? 14 : 12
+                            font.family: Qt.platform.os === "ios" ? "SF Pro Text" : "monospace"
+                        }
+                    }
+                    
+                    Slider {
+                        id: micGainSlider
+                        Layout.fillWidth: true
+                        Layout.preferredHeight: Qt.platform.os === "ios" ? 30 : implicitHeight
+                        from: -20.0
+                        to: 20.0
+                        stepSize: 0.5
+                        value: ReflectorClient.micGainDb
+                        
+                        onValueChanged: {
+                            if (Math.abs(value - ReflectorClient.micGainDb) > 0.1) {
+                                ReflectorClient.micGainDb = value
+                            }
+                        }
+                        
+                        background: Rectangle {
+                            x: micGainSlider.leftPadding
+                            y: micGainSlider.topPadding + micGainSlider.availableHeight / 2 - height / 2
+                            width: micGainSlider.availableWidth
+                            height: Qt.platform.os === "ios" ? 4 : 6
+                            radius: 2
+                            color: isDarkMode ? "#38383A" : "#C6C6C8"
+                            
+                            Rectangle {
+                                width: micGainSlider.visualPosition * parent.width
+                                height: parent.height
+                                color: Qt.platform.os === "ios" ? "#007AFF" : (isDarkMode ? "#4A90E2" : "#0078D4")
+                                radius: 2
+                            }
+                        }
+                        
+                        handle: Rectangle {
+                            x: micGainSlider.leftPadding + micGainSlider.visualPosition * (micGainSlider.availableWidth - width)
+                            y: micGainSlider.topPadding + micGainSlider.availableHeight / 2 - height / 2
+                            width: Qt.platform.os === "ios" ? 28 : 20
+                            height: Qt.platform.os === "ios" ? 28 : 20
+                            radius: Qt.platform.os === "ios" ? 14 : 10
+                            color: Qt.platform.os === "ios" ? "#FFFFFF" : (isDarkMode ? "#FFFFFF" : "#FFFFFF")
+                            border.color: Qt.platform.os === "ios" ? "#C6C6C8" : (isDarkMode ? "#666666" : "#C6C6C8")
+                            border.width: Qt.platform.os === "ios" ? 1 : 1
+                            
+                            // iOS-style shadow
+                            layer.enabled: Qt.platform.os === "ios"
+                            layer.effect: DropShadow {
+                                horizontalOffset: 0
+                                verticalOffset: 1
+                                radius: 3
+                                samples: 7
+                                color: "#40000000"
+                            }
+                        }
+                    }
+                    
+                    RowLayout {
+                        Layout.fillWidth: true
+                        
+                        Label {
+                            text: "-20"
+                            color: isDarkMode ? "#8E8E93" : "#999999"
+                            font.pixelSize: Qt.platform.os === "ios" ? 12 : 10
+                        }
+                        
+                        Item { Layout.fillWidth: true } // Spacer
+                        
+                        Label {
+                            text: "0"
+                            color: isDarkMode ? "#8E8E93" : "#999999"
+                            font.pixelSize: Qt.platform.os === "ios" ? 12 : 10
+                        }
+                        
+                        Item { Layout.fillWidth: true } // Spacer
+                        
+                        Label {
+                            text: "+20"
+                            color: isDarkMode ? "#8E8E93" : "#999999"
+                            font.pixelSize: Qt.platform.os === "ios" ? 12 : 10
+                        }
+                    }
+                }
+                
                 Button {
                     id: connectButton
                     Layout.fillWidth: true
diff --git a/iOS/ReflectorClient.cpp b/iOS/ReflectorClient.cpp
@@ -251,6 +251,10 @@ void ReflectorClient::initializeAudioEngine()
     m_audioEngine = new AudioEngine();
     m_audioEngine->moveToThread(m_audioThread);
     
+    // Initialize AudioEngine with current mic gain setting
+    QMetaObject::invokeMethod(m_audioEngine, "setMicGainDb", Qt::QueuedConnection, 
+                              Q_ARG(double, m_micGainDb));
+    
     // Connect signals from AudioEngine to ReflectorClient
     connect(m_audioEngine, &AudioEngine::audioReadyChanged, this, [this](bool ready) {
         m_audioReady = ready;
@@ -350,6 +354,24 @@ void ReflectorClient::sendHeartbeat()
 QString ReflectorClient::connectionStatus() const { return m_connectionStatus; }
 bool ReflectorClient::pttActive() const { return m_pttActive; }
 QString ReflectorClient::currentTalker() const { return m_currentTalker; }
+
+void ReflectorClient::setMicGainDb(double gainDb) {
+    // Clamp gain to -20dB to +20dB range for safety
+    gainDb = qBound(-20.0, gainDb, 20.0);
+    
+    if (qAbs(m_micGainDb - gainDb) < 0.1) return; // Avoid unnecessary updates
+    
+    m_micGainDb = gainDb;
+    emit micGainDbChanged();
+    
+    // Notify AudioEngine about the gain change if connected
+    if (m_audioEngine) {
+        QMetaObject::invokeMethod(m_audioEngine, "setMicGainDb", Qt::QueuedConnection, 
+                                  Q_ARG(double, gainDb));
+    }
+    
+    qDebug() << "Microphone gain set to:" << gainDb << "dB";
+}
 void ReflectorClient::connectToServer(const QString &host, int port, const QString &authKey, const QString &callsign, quint32 talkgroup) {
     if (m_state != Disconnected) return;
     
@@ -493,6 +515,11 @@ void ReflectorClient::startTransmission() {
 
 #if defined(Q_OS_IOS)
     // iOS microphone permission is handled by the system via Info.plist
+    // SECURITY: Configure audio session to DUCK other apps before PTT
+    // This prevents other audio from mixing into microphone input
+    ios_configureDuckingAudioSession();
+    qDebug() << "iOS: Audio session configured for secure PTT (ducking mode)";
+    
     // Request audio focus equivalent to Android audio focus
     IOSVoIPHandler::instance()->requestAudioFocus();
     qDebug() << "iOS audio focus requested for PTT";
@@ -518,7 +545,7 @@ void ReflectorClient::startTransmission() {
     
     // Start recording through AudioEngine
     QMetaObject::invokeMethod(m_audioEngine, "startRecording", Qt::QueuedConnection);
-    qInfo() << "PTT Pressed: Recording started.";
+    qInfo() << "PTT Pressed: Recording started (secure mode - other apps ducked).";
 }
 void ReflectorClient::pttReleased() {
     if (!m_pttActive) return;
@@ -556,6 +583,13 @@ void ReflectorClient::pttReleased() {
         QMetaObject::invokeMethod(m_audioEngine, "stopRecording", Qt::QueuedConnection);
     }
     
+#if defined(Q_OS_IOS)
+    // RESTORE: Configure audio session to MIX with other apps after PTT
+    // This allows cooperative behavior with music, podcasts, etc.
+    ios_configureMixingAudioSession();
+    qDebug() << "iOS: Audio session restored to cooperative mixing mode after PTT";
+#endif
+    
     // Inform the server that we are done transmitting so talker state can be
     // updated immediately instead of waiting for a timeout.
     QByteArray flush(sizeof(Svxlink::UdpMsgHeader), Qt::Uninitialized);
diff --git a/iOS/ReflectorClient.h b/iOS/ReflectorClient.h
@@ -49,6 +49,7 @@ class ReflectorClient : public QObject
     Q_PROPERTY(bool isDisconnected READ isDisconnected NOTIFY connectionStatusChanged)
     Q_PROPERTY(bool audioReady READ audioReady NOTIFY audioReadyChanged)
     Q_PROPERTY(bool isReceivingAudio READ isReceivingAudio NOTIFY isReceivingAudioChanged)
+    Q_PROPERTY(double micGainDb READ micGainDb WRITE setMicGainDb NOTIFY micGainDbChanged)
 
 public:
     static ReflectorClient* instance();
@@ -62,6 +63,8 @@ class ReflectorClient : public QObject
     bool isDisconnected() const { return m_state == Disconnected; }
     bool audioReady() const { return m_audioReady; }
     bool isReceivingAudio() const { return m_isReceivingAudio; }
+    double micGainDb() const { return m_micGainDb; }
+    void setMicGainDb(double gainDb);
 
     Q_INVOKABLE void connectToServer(const QString &host, int port, const QString &authKey, const QString &callsign, quint32 talkgroup);
     Q_INVOKABLE void disconnectFromServer();
@@ -95,6 +98,7 @@ public slots:
     void txTimeStringChanged();
     void audioReadyChanged();
     void isReceivingAudioChanged();
+    void micGainDbChanged();
     
     // New protocol signals
     void connectedNodesChanged(const QStringList &nodes);
@@ -174,6 +178,7 @@ private slots:
     QString m_connectionStatus = "Disconnected";
     bool m_pttActive = false;
     bool m_audioReady = false;
+    double m_micGainDb = 0.0; // Default 0dB gain (no change)
 
     QTcpSocket* m_tcpSocket = nullptr;
     QUdpSocket* m_udpSocket = nullptr;
diff --git a/iOS/ios/IOSAudioManager.h b/iOS/ios/IOSAudioManager.h
@@ -44,6 +44,11 @@ void ios_acquireScreenWakeLock(void);
 void ios_releaseScreenWakeLock(void);
 int ios_isScreenWakeLockActive(void);
 
+// Audio session cooperation and security functions
+void ios_configureDuckingAudioSession(void);
+void ios_configureMixingAudioSession(void);
+int ios_isAudioSessionSecure(void);
+
 #ifdef __cplusplus
 }
 #endif
@@ -66,6 +71,11 @@ int ios_isScreenWakeLockActive(void);
 - (void)releaseScreenWakeLock;
 - (BOOL)isScreenWakeLockActive;
 
+// Audio session cooperation and security methods
+- (void)configureDuckingAudioSession;
+- (void)configureMixingAudioSession;
+- (BOOL)isAudioSessionSecure;
+
 @property (nonatomic, assign) UIBackgroundTaskIdentifier backgroundTask;
 @property (nonatomic, strong) AVAudioSession *audioSession;
 @property (nonatomic, assign) BOOL screenWakeLockActive;
diff --git a/iOS/ios/IOSAudioManager.mm b/iOS/ios/IOSAudioManager.mm
